The field of the disclosure relates generally to rotary machines, and more particularly, to a blade that includes shank features that facilitate reducing stress peaks and gradients within the shank.
At least some known rotary machines include a compressor, a combustor coupled downstream from the compressor, a turbine coupled downstream from the combustor, and a rotor shaft rotatably coupled between the compressor and the turbine. Some known turbines include at least one rotor disk coupled to the rotor shaft, and a plurality of circumferentially-spaced turbine blades that extend outward from each rotor disk to define a stage of the turbine. Each turbine blade includes an airfoil that extends radially outward from a platform towards a turbine casing.
At least some known turbine blades include a shank and dovetail radially inward of the platform to facilitate coupling the blade to the rotor disk. An operational life cycle of at least some turbine blades is limited at least in part by fatigue induced as a result of a mean stress field and a vibratory stress field converging to form a stress concentration in an interface defined between the blade dovetail and the blade shank.
To facilitate reducing stress concentrations, at least some known turbine blades include dovetail backcuts designed to relieve stresses in the shank-to-dovetail interface. However, because of increased complexity and an associated expense of manufacture of the turbine blade, based on a location and amount of material that must be removed, an effectiveness of using dovetail backcuts may be limited. Additionally or alternatively, at least some known dovetail backcuts require complementary modifications to the rotor disk as well, which also increases the cost of manufacturing.